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Reply-To: yunhanw@nestlabs.com
From:   Yunhan Wang <yunhanw@nestlabs.com>
Date:   Thu, 13 Dec 2018 15:13:26 -0800
Message-ID: <CALvjcs9jRvfb6uFN5BZx26Nh3ojwL5S_Bt08Q72aHPjZUZTtUA@mail.gmail.com>
Subject: Re: BLE advertisement re-enabling after ble connection goes away
To:     Martin Turon <mturon@google.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>
Cc:     linux-bluetooth@vger.kernel.org
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Sender: linux-bluetooth-owner@vger.kernel.org
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Hi, Luiz

Rephrasing a little bit..

From what you describes, it seems Bluez is taking the responsibility
to reenable the advertisement in peripheral side after the previous
ble connection goes
away.

When I did local test, the ble peripheral is using bluez, I create
gatt server and ble advertisment using Bluez DBus API,  when remote
connection in central disconnects, I see kernel in Bluez in peripheral
side do receive
HCI_EV_DISCONN_COMPLETE event, and trigger
hci_req_reenable_advertising.

Maybe you can share the code location where Bluez is reenabling the
advertisement after ble connection goes away?

Thanks
Best wishes
On Thu, Dec 13, 2018 at 3:10 PM Yunhan Wang <yunhanw@nestlabs.com> wrote:
>
> Hi, Luiz
>
> From what you describes, it seems Bluez is taking the responsibility
> to reenable the advertisement after the previous ble connection goes
> away.
>
> When I did local test, the ble peripheral is using bluez, I create
> gatt server and ble advertisment using Bluez DBus API,  when remote
> connection in central disconnects, I see kernel in Bluez do receive
> HCI_EV_DISCONN_COMPLETE event, and trigger
> hci_req_reenable_advertising.
>
> Maybe you can share the code location where Bluez is reenabling the
> advertisement after ble connection goes away?
>
> Thanks
> Best wishes
> Yunhan
>
> On Thu, Dec 13, 2018 at 2:30 PM Martin Turon <mturon@google.com> wrote:
> >
> > Hi Luiz,
> >
> > Is this behavior also expected on raw hci sockets?  Because my observat=
ion is that when working with raw hci over such sockets, auto-reenable does=
 not occur.
> >
> >     #define BTPROTO_HCI                 1
> >     #define HCI_CHANNEL_USER         1
> >
> >     struct sockaddr_hci shci;
> >     shci.hci_family =3D AF_BLUETOOTH;
> >     shci.hci_dev =3D s_ble_hci_device;
> >     shci.hci_channel =3D HCI_CHANNEL_USER;
> >
> >     s =3D socket(PF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI);
> >     rc =3D bind(s, (struct sockaddr *)&shci, sizeof(shci));
> >
> > Also, which API allows the user to control the advertising instances yo=
u describe?  Are they automatically created by the kernel when HCI is sent =
to a raw socket to enable advertising?
> >
> > Thanks,
> > Martin
> >
> > _____________________________
> > Martin Turon  |  Google
> >
> >
> >
> > On Thu, Dec 13, 2018 at 1:49 PM Luiz Augusto von Dentz <luiz.dentz@gmai=
l.com> wrote:
> >>
> >> Hi Yunhan,
> >>
> >> The BlueZ API operates a bit different than HCI, it keeps re-enabling =
the advertisement if there is any instance active, but the user can stop th=
is by removing its instance once a connection is made, this is considered m=
ore convenient than having the user to reprogram the advertisement on every=
 disconnection.
> >>
> >> On Thu, 13 Dec 2018, 18:38 Yunhan Wang <yunhanw@nestlabs.com wrote:
> >>>
> >>> +Martin
> >>>
> >>> Hi, Luiz and Marcel
> >>>
> >>> When I take a look at the bluetooth code, it seems it is re-enabling
> >>> ble advertisement after ble connection goes away. Any idea?
> >>>
> >>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.g=
it/tree/net/bluetooth/hci_event.c#n2634
> >>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.g=
it/tree/net/bluetooth/hci_event.c#n2712
> >>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.g=
it/tree/net/bluetooth/hci_request.c#n1386
> >>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.g=
it/tree/net/bluetooth/hci_request.c#n1734
> >>>
> >>> Thanks
> >>> Best wishes
> >>> Yunhan
> >>> On Wed, Dec 5, 2018 at 6:54 PM Yunhan Wang <yunhanw@nestlabs.com> wro=
te:
> >>> >
> >>> > Hi, Luiz and Marcel
> >>> >
> >>> > May I have a question on ble behavior on BLE re-advertisement?
> >>> >
> >>> > According to Bluetooth spec Vol. 3 (the host volume), 9.2.4.2, "The
> >>> > device shall remain in general discoverable mode until a connection=
 is
> >>> > established or the Host terminates the mode."
> >>> >
> >>> > There is no description on re-enabling the advertising "after"
> >>> > disconnection, so the responsibility for re-enabling the advertisin=
g
> >>> > is bluez or kernel or application code? In other words, does kernel=
 or
> >>> > bluez or application would re-enable the ble advertisement after bl=
e
> >>> > disconnection happens?
> >>> >
> >>> > Thanks
> >>> > Best wishes
> >>> > Yunhan.